Portable power tools having high rate, rechargeable batteries are commercially available. A high rate and rechargeable battery is a nickel cadmium (NiCd) battery. A high rate battery is one that is capable of discharging its entire energy capacity in a relatively short period of time. Tools using high rate batteries are, however, limited because the charge in the high rate battery can be dissipated quickly as a result of use. This requires that the battery be frequently recharged or that additional battery packs be provided if prolonged use is desired. Others have proposed that the useable life of the nickel cadmium battery pack can be extended by mounting additional batteries on articles of clothing. See U.S. Pat. Nos. 3,919,615 and 5,680,026. This solution, however, is obtained at the expense of increased weight arising from additional batteries.
Low rate batteries, for example, lithium ion (Li ion) or nickel metal hydride (NiHM) batteries, are commercially available. But, their use is confined to portable electronic devices, such as telephones, computers and pagers, and their use in power tools has not been suggested because these batteries are unable to provide the current density required to operate a tool.
Accordingly, there is a need to provide a power tool that can be operated for greater lengths of time without dramatic increases in the weight of the tool.